Stainless: SDKs for OpenAI, Anthropic & Meta

The Growing Need for Software Development Kits

Developers commonly anticipate that technology companies will provide software development kits (SDKs) alongside their products. These kits simplify the process of application creation utilizing those products. However, a significant number of vendors currently offer only application programming interfaces (APIs), which are essentially communication protocols for software components.

Stainless: AI-Powered SDK Generation

Alex Rattray, founder of Stainless, believes artificial intelligence offers a solution to this challenge. Stainless employs a compiler to automatically generate SDKs from APIs, doing so dynamically and largely in real-time.

The Challenges of API-Only Access

Without an SDK, users of an API are compelled to meticulously study API documentation and construct all necessary components independently. Creating SDKs at scale, however, presents a considerable hurdle for vendors.

How Stainless Works

Stainless accepts an API specification as input and subsequently generates SDKs in several popular programming languages, including Python, TypeScript, Kotlin, and Go. The platform also manages API evolution, delivering updates with version control and change logs.

AI-Driven Efficiency and Consistency

Traditionally, vendors have relied on internal development teams to build libraries for connecting to their APIs in various languages. Stainless leverages AI to produce an initial configuration, which development teams can then refine. This approach minimizes inconsistencies and obsolescence in libraries, accelerating integration and upgrades.

The Future of APIs and Developer Access

“We are rapidly approaching an era where access to expert-level engineering support is readily available to everyone,” Rattray stated. “This shift will lead to APIs evolving from features for power users to the primary interface for all users. Companies lacking robust APIs will become outdated, much like a restaurant without a website.”

Rattray’s Industry Experience

The development of Stainless’ functionality was heavily influenced by Rattray’s prior professional experiences.

From Stripe to Stainless

Rattray, who majored in economics, began programming as a hobby during his time at UPenn. This led to a position as an engineer on the developer platform team at Stripe. During his tenure at Stripe, he played a key role in revamping API documentation and launching the system powering Stripe’s API client SDK.

Competition in the API-to-SDK Space

Stainless is not alone in offering API-to-SDK generation services. Alternatives include LibLab, Speakeasy, and the established OpenAPI Generator project.

Stainless’ Competitive Advantage: Code Quality

Rattray contends that Stainless provides superior “polish” due to its compiler technology. Many customers who have attempted to use the OpenAPI Generator have found the resulting code quality insufficient, requiring substantial editing and refinement.

Major Tech Companies Adopt Stainless

The platform’s refined output has attracted significant attention from industry leaders, including OpenAI, Anthropic, and Meta, as well as Runway, Groq, Cerebras, Modern Treasury, and Cloudflare. Rattray reports that Stainless currently has “hundreds” of paying customers, with SDK downloads reaching tens of millions weekly.

Pricing and Revenue

The majority of customers subscribe to Stainless’ enterprise tier, which includes premium support and AI-specific features. Publishing a single SDK is free. However, access to multiple SDKs across various programming languages requires a monthly subscription ranging from $250 to $30,000 annually.

Financial Performance and Future Growth

Rattray indicates the company’s annual recurring revenue is approximately $1 million, with profitability within reach. To facilitate growth, Stainless recently secured $25 million in Series A funding led by a16z, with participation from Sequoia, The General Partnership, Felicis, Zapier, and MongoDB.

Expanding the Team and Vision

This new funding, bringing the total raised to around $35 million, will be used to expand Stainless’ 20-person team based in New York. “The business operates efficiently, but we chose to raise capital to accelerate development towards our broader vision,” Rattray explained. “SDKs are merely the initial step – our ultimate goal is to create a comprehensive platform for all developer needs related to APIs.”